1. Field of the Invention
The present invention relates to a phosphor for a plasma display panel, and particularly relates to a phosphor for a plasma display panel enabling to improve color purity and greatly increase light emitting efficiency when this phosphor is used as material for constituting a light emitting layer of the plasma display panel, and also relates to the plasma display panel using this phosphor.
2. Prior Art
Recently, the merchandising stage of a plasma display panel (PDP) as a television receiver instead of a conventional large-sized heavy cathode ray tube (CRT) has been attained and this plasma display panel is widely spreading. The plasma display panel is easily made thin and light in weight from its structural features in comparison with the conventional cathode ray tube. Accordingly, the plasma display panel is highlighted as a receiver for realizing a wall type television requiring a large screen and a thinner thickness.
FIG. 2 is a cross-sectional view schematically showing the structure of the plasma display panel. In the structure of the plasma display panel 1, a front side substrate 2 and a rear side substrate 3 having a light transmitting property such as glass, etc. are oppositely arranged such that a predetermined discharging space 10 is formed. A light emitting layer 5 including particles of a phosphor 4 is formed on an inner surface of the above front side substrate 2. Many anodes 6 and many cathodes 7 each having a stripe shape are arranged on an inner surface of the above rear side substrate 3. Each group of the electrodes 6, 7 is covered with a dielectric layer 8. A surface of this dielectric layer 8 is further covered with a protecting layer 9. The discharging space 10 is set to have about 0.1 mm in height. A mixing gas 11 constructed by helium (He) gas or neon (Ne) gas and several vol. % of xenon (Xe) gas is sealed in the above discharging space 10 to generate an ultraviolet ray for exciting the phosphor 4 in discharging.
In the plasma display panel 1 of the above construction, the phosphor 4 is excited by a vacuum ultraviolet ray (VUV) having 147 nm in wavelength and discharged in resonance with xenon of the mixing gas 11 in the discharging space 10 of the electrodes 6, 7. As a result, visible light is radiated so that a predetermined image is displayed.
A maximum subject of the above plasma display panel (PDP) is conventionally the improvement of an image quality. A vigorous improvement of the plasma display panel is advanced to make consistent luminance showing the brightness of a screen and a contrast ratio as a brightness ratio of white and black. However, no image quality corresponding to that of the cathode ray tube (CRT), etc. is yet obtained at the present time and there is large room for further improving the structure of the plasma display panel and a using material thereof.
A phosphor for a general fluorescent lamp and its improved goods are used as a light emitting material for the plasma display panel (PDP) at present. In a basic principle of the phosphor for the fluorescent lamp, an ultraviolet ray having 254 nm in wavelength is converted to visible light. In contrast to this, in a basic principle of the plasma display panel, an ultraviolet ray having 147 nm in wavelength is converted to visible light. Accordingly, the phosphor for the fluorescent lamp does not necessarily have excellent characteristics as a phosphor for the plasma display panel from such a difference between exciting sources. However, there is no use of the phosphor for converting the ultraviolet ray having 147 nm in wavelength to the visible light except for the plasma display panel. Therefore, at present, it is behind in the development of a new phosphor for the plasma display panel having excellent characteristics.
Conventionally, a phosphor additionally activated by europium of three valences as represented by a general formula Y.sub.2 O.sub.3 :Eu is widely used as a red light emitting phosphor for the plasma display panel (PDP). This phosphor is a rare earth oxide phosphor having a light emitting peak wavelength of 611 nm.
However, when the red light emitting phosphor represented by the above general formula Y.sub.2 O.sub.3 :Eu is excited by an ultraviolet ray having a wavelength of 147 nm, problems exist in that light emitting intensity in a red light region is low and color purity required as a display becomes insufficient. Therefore, when the plasma display panel is formed by including this phosphor within a fluorescent film, a problem exists in that it is extremely difficult to improve light emitting efficiency and color purity of the plasma display panel. Accordingly, it is a technical subject to develop a phosphor having a high light emitting intensity and a high color purity in the red light region.